Apparatus for preliminary treatment of raw material mixed for cement burning



April 17, 1934. Y J 5 FA5T|NG 1,955,277

APPARATUS FOR PRELIMINARY TREATMENT OF RAW MATERIAL MIXED FOR CEMENTBURNING Filed April 28, 1931 4 Sheets-Sheet .1

. gvwentoz April 17, 1934. 1,955,277

APPARATUS FOR PRELIMINARY TREATMENT OF RAW MATERIAL MIXEI? FOR CEMENTBURNING J. 5. FASTING 4 Sheets-Sheet 2 Filed April 28, 1931 Svwemtoz 7MMM April 17, 1934.

APPARATUS FOR PRELIMINARY TREATMENT OF RAW MATERIAL MIXED FOR CEMENTBURNING J. FASTING Filed April 28, 1931 4 Sheets-Sheet 3 April 17, 1934.J. s. FASTING 7 APPARATUS FOR PRELIMINARY TREATMENT OF-RAW MATERIALMIXED FOR CEMENT BURNIN 4 Sheets Sheet 4 Fileq A ri 28, 1951 anventozPatented Apr. 1.7, 1934 PATENT OFFICE APPARATUS FOR PRELIMINARY TREAT-MENT OF RAW MATERIAL MIXED FOR CEIWENT BURNING Johan S. Fasting, Valby,near Copenhagen,

Denmark, assignor to F. L. Smidth & 00., New

York, N. Y., a corporation of New Jersey Application April 28, 1931,Serial No. 533,463

- In Great Britain July 24, 1930 1 Claim.

Various attempts have been made to reduce the operating costs of burningcement and similar materials in rotary kilns, especially by causing thecombustion gases produced in the kiln to 5 come into intimate contactwith the material passing through the kiln. With this end in view therehave been placed in the upper portion or drying zone of kilns used inthe wet process, chains or other bodies of relatively large surfacearea, such bodies serving to collect on their surface a thin layer ofraw slurry, so that the transfer of heat from thecombustion gases to theslurry will be furthered in consequence of the large surface of slurrythus produced and exposed to the combustion gases. A limit is soonreached, however, for the extent to which the heat transferring meanscan be used in this manner, as such bodies will reduce thecrosssectional area of the kiln available for passage of the combustiongases and the raw material, and impede such passage.

The present invention has for its object to utilize, to a far greaterextent than heretofore possible, the method of heat transfer from thecombustion gases to the slurry by allowing the raw slurry to form acoating on carrier bodies which coating is dried and preheated by theheat from combustion gases flowing'past the said bodies and by radiantheat from the walls of the chamber where such action takes place; and,it may be, also by heat previously absorbed by such carrier bodies. V

In accordance with this invention the formation of the coating of slurryon the carrier bodies (chains or other suitable metallic bodies) iseffected outside of the kiln, the carrier bodies being thereafter or atthe same time caused to pass through a drying chamber through which passalso the combustion gases, and being finally freed from their dried and,it may be, also preheated coating of slurry, which is then conveyed tothe kiln or other suitable furnace.

The formation of the coating of slurry on the carrier bodies may beefiected in a portion of the same drying chamber through which thecarrier bodies pass, and the subsequent release of the dried coating ofslurry from the carrier bodies may be effected at some suitable point ofthe chamber. The slurry may be applied to the carrierbodies in variousways, as by immersion of the carrier bodies into the slurry, or thespraying of the slurry on the carrier bodies in liquid state, or bypressing the slurry on the carrier bodies in a plastic state, andvarious mechanical devices may be used for these purposes,

By such drying and preheating of the slurrybefore it enters the kilnseveral advantages can be realized that could not be realized by thearrangeinent of chains or the like in the drying zone of a rotary kiln.By the arrangement here referred to the bodies carrying the slurry canbe disposed in such a manner that the coating of slurry adhering theretowill not be exposed to the risk of being scraped away before it isentirely dry, as would be the case in a rotary kiln. The freecross-sectional area of the slurry-drying chamber may further,independently of the cross-section of the kiln, be made as large asdesired, i. e. so large that the number of carrier bodies may be asgreat as required for attaining the requisite superficial area for theslurry, without thereby creating any excessive resistance to the passageof combustion gases through the chamber. -At the same time alldimculties in conveying the slurry through the drying region will beobviated, because the material passes through this region while clingingto the carrier bodies.

Several embodiments of the invention are illus- Figure 6 is a view invertical section of another embodiment of the invention in which theheating chamber, formed to some extent like a slit furnace or verticalkiln, is interposed between the drying chamber and a rotary Figure 7 isa developed vertical circular section corresponding to those shown inFigs. 3, l and 5 but with a modified means for applying the slurry tothe carrier bodieaand Figures 8 and 9 are views in vertical sectionsoftwo other modifications in which endless chains runni g on rollers areused as carrier bodies for the slurry.

In the embodiment of the invention shown in.

Figs. 1, 2 and 3 the slurry-drying chamber 1 is formed as an annularchannel which communicates with a rotary kiln 1 and encircles the stack2, although it might be wholly outside of the stack. The chamber hasfixed side walls 3' and 3" and a bottom 4 sloping outward, while theannular cover 5 which supports the carrier bodies, here shown as chains6, is arranged to rotate about theaxis of the chamber. The chambercommunicates with the rotary kiln by way of a closed channel 7 extendingfrom the bottom of the chamber to the kiln. This channel serves partlyto convey the combustion gases from the kiln to the drying chamber andpartly to convey the dried raw material from the chamber to the rotarykiln; The cover 5 is supported by wheels 5 on a projecting flange 8 onthe upper edge of the outer wall 3", and is rotated slowly by suitablemeans such as a driving shaft 9 with pulley 10 and a pinion 11 engaginga corresponding circular rack 5" on the cover. Air seals 12 are providedalong both edges of the cover. The chamber communicates with the stackby way of a flue 13, Fig. 3. The path of the combustion gases isindicated by arrows in A part of the chamber is formed as or supports atank 14, Figs. 2 and 3, which may be kept filled with raw slurrysupplied by way of a pipe 15 entering the tank at its bottom. As shownin Fig. 3 the chains 6, as they are drawn over this tank 14 with thecover 5, will sink down into the raw slurry and become coated with alayer of the slurry, and will then be drawn over the right-hand sidewall 16 of the tank and then once more assume their hanging position.After having thus passed through the chamber the chains strike a rod orroller 17 disposed slightly below the cover of the chamber channel, alittle to the left of the tank 14, Fig. 3, and above the channel 7through which the dried slurry is discharged into the rotary kiln. Asthe chains are drawn over the rod or roller 17 they are gradually raisedtowards the cover, and when, in their continued passage, they leave therod or roller 1'7 their movement and their impact against the wall 18 ofthe tank 14,

- will free them from the now dried slurry which will drop through thechannel 7 and down into the rotary kiln.

The cover 5 preferably moves in a direction opposite to that of thecombustion gases, and the drying will, therefore, be effected incounterstream. I

Instead of a stack to produce the requisite draft other draft-creatingmeans may be used, such as a fan.

The construction shown in Fig. 4 differs from that shown in Figs. 1 and3 only in respect of the modified means for coating the carrier bodies 6with slurry. Here the slurry is in fact thrown or sprayed up against thecarrier bodies by means of a number of discs 20 rotating rapidly with ahorizontal shaft 19 and situated above the slurrysupplying pipe 15, insuch a manner that they dip constantly into the slurry.

It may be desirable to draw part of the hot combustion gases directlyfrom the rotary kiln 1 to the stack 2 at the point where the slurry isthus supplied in the form of spray, and where the cross-section of thechannel is filled with fine 'drops of slurry, as the conditions for athorough transfer of heat from the combustion gases to the slurry areespecially favorable at this point where the exposed surface area of theslurry in fine drops is considerable. In order to enable combustiongases to be supplied directly from the rotary kiln, by way of the smokeflue 7 of the lat ter, to such part of the drying chamber an aperture 22with gate 23 is provided at bottom of a partition 21 in the dryingchamber, in such a manner that the quantity of combustion gases used canbe regulated.

In the embodiment shown in Fig. 5 the construction is such as toincrease the utilization of the heat. In the spraying of slurry on tothe highly heated parts a liberal generation of steam will be effected,and in the constructions shown in Figs. 1, 2, 3 and 4 such steam ispermitted to escape directly to the stack, whereby the latent heatcontained in the steam will be wasted. In order that this heat may beutilized the following provision is made in the construction shown inFig. 5. The drying chamber is fitted with a transverse partition 24separating from the rest of the chamber the part where the spraying ofthe slurry takes place. The thus separated part 25 of the chambercommunicates with the discharge flue 13 for the combustion gases fromthe drying chamber to the stack by way of a duct 26 and aheat-exchanging member 27 and duct 28 at the opposite end of suchmember. The heatexchanging member is also traversed by the slurry, andin the construction shown it is assumed to be formed by a cylinder 29with vertical pipes therein and interconnected at top by one or moretransverse pipes 30 terminating at the slurry spraying chamber, and atthe bottom by one or more similar pipes communicatingwith theslurrysupply pipe 31. The slurry will thus pass through said pipes inupward direction, and the same pipes will be swept in downward directionby the steam generated in chamber 25. The steam will be condensed whilegiving off its latent heat, and the water of condensation escapes by wayof a pipe 32 at the bottom of the heat-exchanging member.

As mentioned above the preliminary drying devices may be used not onlyin connection with a rotary kiln but also in connection with a shaftfurnace or vertical kiln or the like.

Fig. 6 shows such an arrangement in connection with a shaft furnace. Theslurry is here applied to the carrier bodies by spraying as in Fig. 4,but a connecting flue 33 in shape of a shaft furnace is interposedbetween the drying chamber 4 and the rotary kiln 1.v This flue is formedwith two vertical walls 34 and 35, the wall 34 being joined to thebottom 4 of the drying chamber by means of an inclined plane 36, in sucha manner that all the dried material dropping down from the carrierbodies must pass through the space between the two walls, at the loweredge of which the material is conveyed into the rotary kiln by means ofa conveyor worm 37. The walls 34 and 35 are fitted with downward slopingpassages 38 for the combustion gases escaping from the rotary kiln tothe drying chamber, and the descending dried raw material is thereforeexposed to intense heating between the walls. As mentioned above,however, the burning proper is preferably effected in the rotary kiln 1,as a furnace of this construction produces a more uniform burning thandoes a shaft furnace. This rotary kiln, however, can be relatively shortin comparison with ordinary rotary kilns, in which also the drying or inany case the preheating of the raw material must be effected. Theremaining function of the rotary kiln will then be to take care of thelast part of the thermic treatment of the raw material, mainly thecalcination and the burning.

The embodiment shown in Fig. 7 is intended for use in cases where the'raw material is worked according to the wet method, i. e. in the shapeof raw meal. In this construction the raw material is moistened in onecompartment of the drying chamber, between the supply and the dischargeflue for the combustion gases, by means bit of a worm 39 disposed thereand serving to mix and moisten the raw meal with water supplied bysprinkling from a water pipe 40. Above this worm 39 there is provided aroller or drum 41 conveying the moistened raw material up to the carrierbodies 6 and pressing it against the same, while they are passing alongover the drum. During their passage through this part of the dryingchamber the carrier bodies are supported by guide rolls 42 provided justbelow the cover of said chamber. Instead 01' a drum other means forapplying the moistened raw meal may be used.

-In the embodiment illustrated in Fig. 8 the slurry-carriers are endlesschains 43 placed side by side and running over a driving roll or roller44 disposed at the top and guide rolls or rollers 45,. 46 disposed atthe bottom, one of these being located just above the bottom of a slurrytank 47 and the other above the surface of the slurry contained therein.The chains run further about a guide roll or roller 48 outside of theslurry tank and over a non-cylindrical or eccentrically disposed rotarymember 49 below the slurry tank. The chains 43, the rolls or rollers 44,45, 46, 48 as well as the member 49 and the slurry tank 47 are allenclosed in a casing 50 with an inlet 51 for the combustion gases, whichpass through the casing in the direction of the arrows, and with anoutlet 52 for the gases and for the steam generated from the slurry inthe casing, and with a supply pipe 53 for the slurry and a dischargepipe .54 for the steam generated by the passage, through the slurrybath, of the intensely heated chains. Within the casing is disposed apartition 55 which absorbs heat from the combustion gases and byradiation transfers this heat to the chains and the slurry adheringthereto. The slurry dried on the chains will be dislodged from thechains by the vibrations caused by the rotary member 49, and will dropout through the bottom of the casing. The steam which escapes at ,a hightemperature by way of the discharge pipe 5imay be utilized for variousposes, as for 1 horliejjkheating the slurry introduced into the slurryin the embodiment illustrated in Fig. 9 the same principal arrangementwill be found as that shown in Fig. 8, but with the addition of aspecial device for freeing the slurry coating, on the lower portions ofthe chain as they leave the slurry tank, from a considerable part of itswater; by utilization of the heat contained in the chains and the slurrycoating itself. The heat of the combustion gases will thereby beconserved for evaporation of the renmant of water left in the slurry. Onaccount of the lowered temperature of the chains after utilization oftheir own heat, the heat of the combustion gases can be utilized down toa lower degree of temperature than by the arrangement shown in Fig. 8.In the arrangement shown in Fig. 9 there are provided, inside of thecasing 50 and outside of the lower portion of the said chains, twocooling plates 56, which are constantly sprinkled with cooling waterfrom a supply pipe 57, the said cooling water escaping by way of adischarge pipe 58. The space between the cooling surfaces, between whichthe chains ascend, is fitted with a discharge pipe 59 for the water thatis given oil? as steam from the chains and is condensed on the opposingfaces of the cooling surfaces.

The outlet 52' for the combustion gases is here situated about midway onone side wall of the casing, and the partition 55 inserted in the casingextends all the way down to the slurry tank, so that the combustiongases first sweep up along one side of the partition 55 and then downalong the other side. By this arrangement a better utiliza- I 5 tion ofthe heat of the combustion gases leaving the kiln can be realized thanby the arrangement shown in Fig. 8, and the combustion gases escapingfrom the casing by way oi the outlet 52' will also contain considerablyless water, a substantial part of the water being removed between thecooling surfaces 56..

I claim as my invention:

The combintion with a kiln for the bur oi cement raw material ofapparatus for treating cement raw material preliminary to itsintroduction into the kiln, which comprises a chamber, including atanlr, means to supply liquid raw material to the tank, a series oicarrier bodies, means to move the carrier bodies through the chamber andthe tank, means to direct the combustion gases from the lriln into saidchamber, means to separate the dried raw material from the carrierbodies and means to discharge the separated material into the lid ldb

